I did hear somewhere else that they said the "red" level races were exceptionally difficult, and I will admit that I never bothered racing them (except the freeway ones). There's a bunch of events that don't NEED to be beaten in order to get to 100% and as far as I can tell exist only to 1) give you more money/rep; 2) train your racing skills.

I am a pretty good racer, the best amongst my friends, so I can see where someone with less skill would get upset at the difficulty of the game since I know I had trouble with a few sections, but I still wouldn't rank it as a "difficult" game.